Fluid actuating device for an electric circuit breaker

ABSTRACT

A fluid actuating device for an electric switching apparatus such as a high-voltage power circuit breaker or the like includes an actuator for actuating the electric switching apparatus. The actuator has an actuator cylinder and a differential piston movable in the cylinder between first and second end-positions corresponding to the open and closed positions respectively of the switching apparatus. The differential piston has two endfaces for receiving fluid pressure force. One of the end-faces has a surface area greater than the other end-face thereof. A reservoir supplies fluid under high pressure to the two end-faces of the piston. A valve is provided for alternately interrupting and passing the fluid from reservoir to the larger area end-face whereby the piston is caused to move from the second end-position to the first end-position when the valve interrupts fluid to the larger area end-face. An opening formed in the actuator cylinder conducts fluid to and from the variable volume chamber conjointly defined by the larger end-face and the cylinder. A damping arrangement reduces the speed of the piston in the course of the movement of the same toward the first end-position and before the first end-position is reached. The damping arrangement includes an ancillary piston projecting from the larger area end-face of the differential piston which is received in the opening for interrupting the flow of fluid passing therethrough from the chamber before the piston reaches the first end-position. This action causes the fluid remaining in the chamber to be conducted away through a bypass whereby the speed of the differential piston is reduced. A second bypass is connected in parallel with the first-mentioned bypass and the valve includes means for controlling the passage of fluid through the second bypass to get fluid to the larger area end-face while the ancillary piston is still in the opening during the first part of a movement of the differential piston to the second end-position from the first end-position.

United States Patent Grieger et al.

[ FLUID ACTUATING DEVICE FOR AN ELECTRIC CIRCUIT BREAKER [75] Inventors: Gerhard Grieger; Joaquin Bohrdt,

both of Berlin, Germany [73] Assignee: Siemens Aktienge' !lschaft, Munich,

Germany [22] Filed: July 2, 1973 [21] Appl. No.: 375,747

[30] Foreign Application Priority Data July 13, i972 Germany 2234812 [52] US. Cl. 91/26; 91/25; 91/408; 91/416; 91/417; 200/82 B [51] Int. Cl... FlSb 15/22; Fl5b 15/17; HOlh 35/38 [58] Field of Search 91/25, 26, 408, 409, 416, 91/417, 235, 321; 200/82 B [56} References Cited UNITED STATES PATENTS 2,900,960 8/1959 Gratzmuller 9l/4l7 X 3,l05,l26 9/1963 Peek et al. 9l/4l7 X 3,208,720 9/1965 Huntington.... l37/625.66 X 3,229,958 1/1966 Borel 9l/4l7 X 3,450,003 6/1969 Nightingale 91/26 Primary Examinerlrwin C. Cohen Attorney, Agent, or Firml(enyon & Kenyon Reilly Carr & Chapin [57] ABSTRACT A fluid actuating device for an electric switching apparatus such as a high-voltage power circuit breaker or the like includes an actuator for actuating the elec- 5 51 May 27, 1975 tric switching apparatus. The actuator has an actuator cylinder and a differential piston movable in the cylinder between first and second end-positions corresponding to the open and closed positions respectively of the switching apparatus. The differential piston has two end-faces for receiving fluid pressure force. One of the end-faces has a surface area greater than the other end-face thereof. A reservoir supplies fluid under high pressure to the two end-faces of the piston. A valve is provided for alternately interrupting and passing the fluid from reservoir to the larger area endface whereby the piston is caused to move from the second end-position to the first end-position when the valve interrupts fluid to the larger area end-face. An opening formed in the actuator cylinder conducts fluid to and from the variable volume chamber conjointly defined by the larger end-face and the cylinder. A damping arrangement reduces the speed of the piston in the course of the movement of the same toward the first end-position and before the first end-position is reached. The damping arrangement includes an ancillary piston projecting from the larger area endface of the differential piston which is received in the opening for interrupting the flow of fluid passing therethrough from the chamber before the piston reaches the first end-position. This action causes the fluid remaining in the chamber to be conducted away through a bypass whereby the speed of the differential piston is reduced. A second bypass is connected in parallel with the first-mentioned bypass and the valve includes means for controlling the passage of fluid through the second bypass to get fluid to the larger area end-face while the ancillary piston is still in the opening during the first part of a movement of the differential piston to the second end-position from the first end-position.

PATENTED MAY 2 7 I975 SHEEI FLUID ACTUATING DEVICE FOR AN ELECTRIC CIRCUIT BREAKER BACKGROUND OF THE INVENTION The invention relates to an actuating device for an electric switching apparatus such as an electric circuit breaker, particularly, a high-voltage power circuit breaker. The actuating device includes an actuator having a differential piston and a cylinder and is exposed to pressure at least in part by means of a valve arrangement. A damping device reduces the piston velocity prior to reaching one of its end-positions when the large-area side of the piston is relieved of pressure.

A fluid actuating device of the foregoing type is disclosed, for example, in the copending United States patent application of Gerhard Grieger and Joaquin Bohrdt entitled: FLUID ACTUATING DEVICE FOR AN ELECTRIC CIRCUIT BREAKER.

Hydraulic actuating devices for electric circuit breakers, and in particular, for high-voltage power circuit breakers, must move the movable contacts as fast as possible and without delay in dependence on the control command for closing or opening the breaker. The movable contacts of modern, high-speed highvoltage power circuit breakers can weigh several kilograms and, to move these contacts, an energy of several meter-kilograms is required for the drive. Therefore, the differential pistons of hydraulic actuating devices must be transferred from their one end-position to the other end-position with considerable acceleration. To prevent rebound, the piston motion must be decelerated in a suitable manner over a short stroke.

It is known to provide the differential piston with a damping device which becomes effective shortly before reaching the end-position. In this case, a damping piston connected with the differential piston is introduced into a bore which influences, by means of defined discharge orifices, the discharge velocity of the cylinder contents of the bore, compressed by the damping piston, in the sense of decelerating the piston.

The known arrangements have the drawback that not only the velocity of the differential piston is damped before it reaches the end position, but that also, the starting motion is initially impeded by the damping piston; this leads to a lengthening of the reversal time, that is, the switching time.

SUMMARY OF THE INVENTION It is an object of the invention to provide a fluid actuating device which overcomes the foregoing disadvantages.

The invention achieves the foregoing object by providing that the differential piston is connected with a piston of a damping arrangement which engages, shortly before reaching the end position, with a bore, which is formed in the cylinder opposite the large-area end-face of the piston and which carries the pressure fluid of the actuator cylinder. The pressure medium thereby enclosed in the actuator piston is discharged through a bypass including a throttle point. Parallel to this first bypass is connected a second bypass which is controlled by the valve arrangement. This makes it possible to construct the valve arrangement for controlling the drive as a reversing valve (three-way valve) which, in addition to an inlet-valve body and an outlet valve body for the actuator, is provided with a slide-valve member which opens and closes the second bypass in the same sense as the inlet valve body. During the start ing motion, that is, when the inlet valve body is opened, pressure medium can get, in this manner, into the actuator cylinder space unimpeded and bypassing the damping arrangement so that the starting motion can take its course uninfluenced by the damping arrangement.

The fluid actuating device of the invention is suitable for a switching apparatus such as a highvoltage power circuit breaker or the like. The fluid actuating device includes as a feature an actuator for actuating the electric switching apparatus. The actuator has an actuator cylinder and a differential piston movable in the cylinder between first and second endpositions corresponding to the open and closed positions respectively of the switching apparatus. The differential piston has two end-faces for receiving fluid pressure force and one of the end-faces has a surface area greater than the surface area of the other one of the two end-faces. Highpressure supply means supplies fluid to the two endfaces and valve means alternately interrupts and passes the fluid from'the fluid supply means to the larger area end-face whereby the differential piston is caused to move from the second end-position to the first endposition when the valve means interrupts fluid to the larger area endface thereby relieving the fluid pressure thereon. The larger area end-face of the differential piston and the portion of the actuator cylinder facing towards the larger area end-face conjointly define a chamber having a volume that changes in dependence upon the movement of the piston in the actuator cylinder. Passage means is formed in the actuator cylinder for conducting fluid to and from the chamber in accordance with the movement of the piston between the end-positions. Damping means are provided for reducing the speed of the piston in the course of the movement of the same toward the first end-position from the second end-position and before the first end-position is reached. The damping means includes a bypass for conducting fluid away from the chamber, and an ancillary piston projecting from the larger area end-face of the differential piston. The passage means is an opening configured to accommodate and receive the ancillary piston therein for interrupting the flow of fluid passing therethrough from the chamber before the differential piston reaches the first end-position thereby causing the fluid remaining in the chamber to be conducted away through the bypass whereby the speed of the differential piston is reduced. A second bypass is connected in parallel with the first-mentioned bypass. Also, the valve means includes means for controlling the passage of fluid through the second bypass thereby getting fluid to the larger area end-face of the piston during the time the ancillary piston is still in the opening during the first part of a movement of the differential piston to the second end-position from the first end position.

In addition to the advantages evident from the foregoing, there is the advantage that the damping action is achieved without check valves.

According to another feature of the invention, throttle means can be provided for adjusting the flow of fluid through the bypass first-mentioned above. The throttle means can be a screw adjustably penetrating the bypass for adjusting the cross-section thereof.

The valve arrangement includes advantageously a differential piston acted upon by pressure fluid, and a cylinder, which is combined with the actuator cylinder to form a structural unit.

Thus, the fluid actuating device of invention can include a housing and the actuator cylinder can be formed in this housing. The valve means can include a movable member configured as a differential piston having two end-faces fluidly connected to the fluid supply means. The valve means can further include means for interrupting and passing fluid from the fluid supply means to one of the end-faces of the last-mentioned differential piston. A second cylinder formed in the housing can accommodate the last'mentioned differential piston therein whereby the second cylinder and the ac tuator cylinder are contained in the same structural unit. In this manner, long pipelines for conducting the pressure medium can be avoided, so that pressure losses can be prevented and the intrinsic time for reversing the actuator reduced.

The invention makes it possible to provide effective damping action for the differential piston of the actuator when the breaker opens and still obtains a starting speed when the breaker closing operation is initiated.

Although the invention is illustrated and described herein as an improved fluid actuating device for an electric circuit breaker, it is nevertheless not intended to be limited to the details shown, since various modifications may be made therein within the scope and the range of the claims. The invention, however, together with additional objects and advantages will be best understood from the following description and in connec tion with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a schematic diagram, partially in section, of a fluid actuating device according to the invention. The fluid actuating device is equipped with means for damping the travel of the differential piston as it approaches the end-position thereof corresponding to the open position of the breaker. The actuator differential piston is shown in the position for the breaker open condition.

FIG. 2 is also a schematic diagram and shows the embodiment according to FIG. 1 wherein the differential piston is disposed at its end-position corresponding to the condition of the circuit breaker in the closed posi- IlOl'l.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION FIG. 1 shows an electric power circuit breaker 1 which can, for example, be constructed as a blastpiston circuit breaker with sulfur hexafluoride as the quenching medium and which has a switching capacity of GVA at a voltage of 110 kV or more. The circuit breaker is operated by a hydraulic actuating device 2 which comprises an actuator 5 consisting of a differential piston 3 and an actuator cylinder 4. Pressure can be admitted to the actuator 5 through a valve arrangement 6. The pressure fluid is taken from high-pressure fluid supply means in the form of a reservoir 7 wherein a predetermined pressure is maintained by means of a pump (not shown). The differential piston of the actuator 5 is coupled with the movable contact of the circuit breaker I by means of a piston rod 8.

The pressure fluid is fed to the cylinder 4 of the actuator from the reservoir 7 through a line 9. The fluid is supplied to a line 11 which leads to valve means in the form of the valve arrangement 6. The valve arrangement 6 consists of a differential piston which is rigidly connected with an inlet-valve body 12 and an outlet-valve body 13 for opening and closing correspond- 5 ing inlet-valve and outlet-valve passages of the actuator. The inlet and outlet valve bodies 12 and 13 are attached at opposite ends of a rod 14 which connects the two bodies firmly with each other. The valve arrangement 6 is configured as a reversing valve (three-way valve).

The differential piston 3 is connected with a plugshaped piston 15 which engages with a cylinder bore 16. The endface 18 of the cylinder 4 adjacent the largearea end-face 17 of the differential piston 3 also has a bore 19 which constitutes a first bypass and is equipped with a throttle means 20. An outlet 21 leading from throttle means and the bypass 19 opens into the space 22 formed between the inlet and outlet valve seats. The bore 16 also opens into the space 22.

From the end-face 18 of the cylinder 4, a second bypass 23 leads into the space 22. The opening 24 of the second bypass can be controlled by a slide-valve member 25, which is firmly mounted on the rod 14. This slide-valve body 25 is operated in the same sense as the inlet-valve body 12. That is, slide-valve body 25 opens the bypass 23 when the inlet valve opens, and closes the bypass 23 when the outlet valve opens and the inlet valve closes.

The operation of the fluid actuating device according to the invention is as follows:

For reversing the actuator 5 from the position seen in FIG. 2 into the open position of the electric circuit breaker l, the line 10a leading to the differential piston 10 is relieved of pressure. The differential piston 10 thereupon occupies the position that can be seen in FIG. 1, so that the inlet valve 12 is closed. At the same time, the slide-valve body 25 is moved in front of the opening 24 of the second bypass 23. The pressure medium supplied from the reservoir 7 to the actuator cylinder 4 through the line 9 acts on the small-area endface 17a of the differential piston 3 and moves the latter downward. In the course of its motion, the plugshaped piston 15 enters the bore 16 and thereby encloses between the actuator cylinder 4 and the piston 3 a volume of pressure fluid that can flow out only through the bypass 19 having an adjustable crosssection. The discharge during the entire piston movement takes place through the outlet valve 13 and a line 26, the line 26 being connected with a low-pressure tank 27 for the pressure medium. In this manner, the opening motion of the differential piston 3 is effectively damped shortly before it reaches the end position.

If the differential piston is again reversed from the position shown in FIG. 1 by applying pressure to the differential piston 10 through the line 10a, pressure fluid is fed by the opening of the inlet-valve body 12 from the reservoir 7 through the lines 9 and 11 to the bore 16 as well as, through the second bypass 23, to the large-area end-face 17 of the differential piston 3. In this manner, the damping arrangement 19, 20 is made ineffective, more specifically, the starting motion takes place uninfluenced by this damping arrangement.

As shown in FIGS. 1 and 2, the valve arrangement 6 is composed of a differential piston 10 which can be acted upon by a pressure medium, and a cylinder 10b, which is combined with the actuator cylinder 4 to form a structural unit. Thus, in this way, it is possible to combine in one structural unit, the essential lines and bores which carry the pressure fluid and serve to reverse the actuator 5.

What is claimed is:

l. A fluid actuating device for an electric switching apparatus such as a high-voltage power circuit breaker or the like comprising: an actuator for actuating the electric switching apparatus; said actuator including an actuator cylinder, and a differential piston movable in said cylinder between first and second end-positions corresponding to the open and closed positions respectively of the switching apparatus, said differential piston having two end-faces for receiving fluid pressure force, one of said end-faces having a surface area greater than the surface area of the other one of said two end-faces; high-pressure supply means for supplying fluid to said two end-faces; valve means for alternately interrupting and passing the fluid from said fluid supply means to said one end-face whereby said differential piston is caused to move from said second endposition to said first end-position when said valve means interrupts fluid to said one end-face thereby relieving the fluid pressure thereon; said one end-face of said differential piston and the portion of said actuator cylinder facing towards said one end-face conjointly defining a chamber having a volume that changes in dependence upon the movement of said piston in said actuator cylinder; passage means formed in said actuator cylinder for conducting fluid to and from said chamber in accordance with the movement of said piston between said end-positions; damping means for reducing the speed of said piston in the course of the movement of the same toward said first end-position from said second end-position and before said first end-position is reached, said damping means including: a bypass for conducting fluid away from said chamber, an ancillary piston projecting from said one end-face of said differential piston, said passage means being an opening configured to accommodate and recieve said ancillary piston therein for interrupting the flow of fluid passing therethrough from said chamber before said differential piston reaches said first end-position thereby causing the fluid remaining in said chamber to be conducted away through said bypass whereby the speed of said differential piston is reduced; 21 second bypass connected in parallel with said first-mentioned bypass; said actuator including a valve-inlet passage for directing fluid from said fluid supply means to said one end-face of said differential piston, and a valve-outlet passage for directing fluid away from said one end-face; and, said valve means comprising a member movable between first and second positions, two valve bodies forming part of said member and corresponding to respective ones of said passages for opening and closing the same in dependence upon the position of said member, and a slidevalve body also forming part of said member for opening and closing said second bypass in the same sense as said valve-inlet passage in opened and closed and so controls the passage of fluid through said second bypass thereby getting fluid to said one end-face of said piston during the time said ancillary piston is still in said opening during the first part of a movement of said differential piston to said second end-position from said first end-position.

2. The fluid actuating device of claim 1 comprising throttle means for adjusting the flow of fluid through said first-mentioned bypass.

3. The fluid actuating device of claim 2, said throttle means being a screw adjustably penetrating said firstmentioned bypass for adjusting the corss-section thereof.

4. The fluid actuating device of claim 1 comprising a housing, said actuator cylinder being formed in said housing, said movable member being configured as a differential piston having two end-faces fluidly connected to said fluid supply means; and, said valve means further comprising means for interrupting and passing fluid from said fluid supply means to one of said end-faces of said last-mentioned differential piston, and a second cylinder formed in said housing for accommodating said last-mentioned differential piston therein whereby said second cylinder and said actuator cylinder are contained in the same structural unit,

* t IIK 

1. A fluid actuating device for an electric switching apparatus such as a high-voltage power circuit breaker or the like comprising: an actuator for actuating the electric switching apparatus; said actuator including an actuator cylinder, and a differential piston movable in said cylinder between first and second end-positions corresponding to the open and closed positions respectively of the switching apparatus, said differential piston having two end-faces for receiving fluid pressure force, one of said end-faces having a surface area greater than the surface area of the other one of said two endfaces; high-pressure supply means for supplying fluid to said two end-faces; valve means for alternately interrupting and passing the fluid from said fluid supply means to said one end-face whereby said differential piston is caused to move from said second end-position to said first end-position when said valve means interrupts fluid to said one end-face thereby relieving the fluid pressure thereon; said one end-face of said differential piston and the portion of said actuator cylinder facing towards said one end-face conjointly defining a chamber having a volume that changes in dependence upon the movement of said piston in said actuator cylinder; passage means formed in said actuator cylinder for conducting fluid to and from said chamber in accordance with the movement of said piston between said endpositions; damping means for reducing the speed of said piston in the course of the movement of the same toward said first endposition from said second end-position and before said first endposition is reached, said damping means including: a bypass for conducting fluid away from said chamber, an ancillary piston projecting from said one end-face of said differential piston, said passage means being an opening configured to accommodate and recieve said ancillary piston therein for interrupting the flow of fluid passing therethrough from said chamber before said differential piston reaches said first end-position thereby causing the fluid remaining in said chamber to be conducted away through said bypass whereby the speed of said differential piston is reduced; a second bypass connected in parallel with said first-mentioned bypass; said actuator including a valve-inlet passage for directing fluid from said fluid supply means to said one end-face of said differential piston, and a valve-outlet passage for directing fluid away from said one end-face; and, said valve means comprising a member movable between first and second positions, two valve bodies forming part of said member and corresponding to respective ones of said passages for opening and closing the same in dependence upon the position of said member, and a slide-valve body also forming part of said member for opening and closing said second bypass in the same sense as said valve-inlet passage in opened and closed and so controls the passage of fluid through said second bypass thereby getting fluid to said one end-face of said piston during the time said ancillary piston is still in said opening during the first part of a movement of said differential piston to said second endposition from said first end-position.
 2. The fluid actuating device of claim 1 comprising throttle means for adjusting the flow of fluid through said first-mentioned bypass.
 3. The fluid actuating device of claim 2, said throttle means being a screw adjustably penetrating said first-mentioned bypass for adjusting the corss-section thereof.
 4. The fluid actuating device of claim 1 comprising a housing, said actuator cylinder being formed in said housing, said movable member being configured as a differential piston having two end-faces fluidly connected to said fluid supply means; and, said valve means further comprising means for interrupting and passing fluid from said fluid supply means to one of said end-faces of said last-mentioned differential piston, and a second cylinder formed in said housing for accommodating said last-mentioned differential piston therein whereby said second cylinder and said actuator cylinder are contained in the same structural unit. 